The present invention deals with a method and system for improving high speed internetwork data transfers. More particularly, the invention is intended to interconnect Token ring/IP Hosts over Token ring Local Area Networks (LAN) and a Wide Area Network (WAN) by creating one way bridged path for host-to-host connections, using IP routing protocols to create the path, so that the LAN virtually enlarges till it encompasses the WAN with bridging getting everywhere.
Modern digital networks are made to operate over different transmission media and interconnect, upon request, a very large number of users and applications through fairly complex digital communication networks.
Accordingly, due to the variety of users"" profiles and distributed applications, the corresponding traffic is becoming more and more bandwidth consuming, non-deterministic and requiring more connectivity. This has been the driver for the emergence of fast packet switching techniques in which data from multimedia origin are chopped into fixed length packets (e.g. in Asynchronous Transfer Mode (ATM) type of operation) or in variable length packets (e.g. in so called Frame Relay (FR) type of operation). These packets are then transferred upon request for communication purposes between data sources and targets via so-called high speed communication networks. One of the key requirements for high speed packet switching networks is to reduce the end to end delays.
Also, due to the incredible increase of traffic, several types of networks have been installed which need to be interconnected to optimize the possibilities of organizing traffic between a source host terminal and a target host terminal, both located anywhere. This is made possible by using so-called internetworking (also referred to as internet). An internet is a collection of heterogeneous networks using a set of networking protocols (TCP/IP, i.e Transmission Control Protocol/Internet Protocol) developed to allow cooperating computers to share resources across the network. TCP/IP products are made by vendors and a fairly large number of networks of all kinds use it. Accordingly, the considered IP switching technologies may incorporate new proprietary protocols, which complicates inter-networking operations.
TCP/IP is a set of data communication protocols that are referred to as the internet protocol (IP) suite. Because TCP and IP are the best known of the protocols, it has become common to use the term TCP/IP to refer to the whole family. TCP and IP are two of the protocols in this suite. Other protocols that are part of the internet suite are User Datagram Protocol (UDP), Internet Control Message Protocol (ICMP), Address Resolution Protocol (ARP), Real Time Protocol (RTP) and Reservation Protocol (RSvP).
An Internet is a collection of heterogeneous networks using TCP/IP. The administrative responsibilities for an internet (for example, to assign IP addresses and domain names) can be within a single group or distributed among multiple groups. Networks comprising an internetwork can use either the same or different technologies.(For more information on TCP/IP one may refer to the book xe2x80x9cInternet working with TCP/IPxe2x80x9d by Douglas Comer).
Host stations attached to LANs can send messages from any of them to any other. Communication within a single (LAN) network is referred to as intranetworking, and communications between stations that are attached to different LAN networks is called internetworking. Stations within a same network can communicate directly, while internetworking communications have to go across special internetworking devices called gateways and possibly referred to as routers as they route data from one network into another.
As shall be emphasized in the following description, the routers may, in some cases be replaced by so-called bridges. Both have specific characteristics as they operate at different layers of protocols of the network.
As networks have developed, various approaches have been used in the choice of communication characteristics such as communication medium, network topology, message formats, protocols for channel access etc . . . . Some of these approaches have been converted into standards. A model of these standards is known as the International Standards Organization (ISO) Open System Interconnection (OSI) model. This model specifies a hierarchy of protocol layers and defines the function of each layer in the considered network. Each layer in one station which might be a host computer or a Router/Bridge carries a conversation with the corresponding layer in another station with which communication is taking place, in accordance with the protocol defining the rules of this communication. In fact, information is transferred down from layer to layer in one host or router then through the channel medium and back up the successive layers in the other host or router/bridge (target). Accordingly, the higher the layer at which communication operations are performed, the longer and more cycle consuming the process.
IETF standardizes TCP/IP through RFCs (Requests For Comments).The three layers (out of seven) defined by the OSI Standards and to be considered here include the physical layer, the data link layer and the network layer. The physical layer is the lowest layer (i.e level 1) assigned to transmission of data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering, depending on the physical medium used to build the communication channel.
The layer next to the physical layer, is the data link layer (i.e. level 2). The main task of the data link layer is to transform the physical layer interfacing with the channel into a communication link that appears error-free to the next above layer, i.e. the network layer (level 3). The data link layer performs such operations as structuring data into packets or frames and attaching control information and numbers to the packets or frames to enable checking data validity and reinserting reconstructed packets at the right location into the data flow. There are two point-to-point types of connections i.e. connectionless and connection oriented connections.
Although the data link layer is primarily independent of the nature of the transmission medium, certain aspects of the data link layer functions are dependent on the transmission medium. This is why, in some network architectures, the data link layer is divided into two sublayers: a logical link control sublayer which performs all medium-independent functions of the data link layer, and Media Access Control (MAC) sublayer. The MAC sublayer determines which station should get access to the communication channel, when requests for access are in conflict. The functions of the MAC sublayer are more likely to be dependent on the transmission medium. Bridges may be designed to operate in the MAC sublayer.
As internetwork topologies become more and more complex, the number and significance of routers or bridges used to interconnect the network both increase. Consequently, the choice between these two devices for performing the interconnecting function may seriously impact the whole internetwork performance, e.g. in terms of transmission time delay.
The basic function of a bridge is to make large interconnected networks look like a single flat LAN. A bridge acts at the MAC layer and listens to all message traffic on all networks (e.g. LANs) to which it is connected, and forwards each message onto the networks other than the one from which the message was received. Bridges also maintain a database of station locations derived from the content of the messages being forwarded. After a bridge has been in operation for some time, it can associate practically every station with a particular link (i.e. path) connecting the bridge to a network (e.g. LAN) which contributes to speeding up the traffic.
There are two main types of bridges which are: Transparent Bridges (TB) and Source Route Bridges (SRB). There are also combinations of these (SRTB).
If several networks are connected by bridges and form a closed loop, a message may be circulated back to the network from which it was originally transmitted, which may flood the internetworking facility and jam the traffic. To prevent the formation of such closed loop, a so called Spanning Tree algorithm has been developed to connect the bridged networks into a tree configuration containing no closed loops. The spanning tree algorithm is executed periodically by the bridges on the interconnected network to ensure that the tree structure is maintained up-to-date, even if the physical configuration of the network changes.
While the basic advantage of the bridge (i.e. transparency to layer 3) is the rapidity of message transfers, these transfers operating at data link level (i.e. layer 2), some traffic overflow may be due to bridge transparency. For instance this is the case with TCP/IP traffic caused by so-called Address Resolution Protocol (ARP) messages made to obtain, when required, a data link layer address from the corresponding network layer address. ARP packets can be duplicated by bridges and storm the whole internetwork, possibly disrupting normal traffic flow. But as far as this invention is concerned it should essentially be recalled that bridges are transparent to broadcast messages which shall then multiply and propagate through the whole internetwork.
A router unlike a bridge, operates at the network layer level (layer 3) instead of the data link layer level, and is fundamentally meant to interconnect unlike network technologies and provide a structured address space (routing based on global address). Addressing at the network layer level, as obtained by the content of data packet address field includes a unique network identifier and a target identifier within the network. A router learns the topology of the network and builds a routing table to represent it. IP tables are established manually or through routing protocols (RIP, OSPF etc . . . ), where routers learn how to reach networks.
Routers make use of the destination network identifier in a message to determine an optimum path from the source network to the destination network. But as far as the present invention is concerned it should be noted that broadcasted messages shall be stopped by any reached router. Consequently routers provide a better isolation than bridges at the expense of processor utilization.
Thus, the network designer has to deal with conflicting situations and choose between routing and bridging operations.
Compromises to these kinds of situations have been proposed in the art. Some have an impact on source and/or target hosts software. Given the fairly wide variety of hosts already in the field no simple and unique solution to the problem raised may be proposed. Other solutions, like for instance the solution recommended by U.S. Pat. No. 5,309,437, address extended LANs and use so-called bridge-like routers including both functions. Then, depending on the type of traffic, either one of the functions is called for use. Unfortunately, during ARP operation all normal traffic is made to suffer. An improved solution to internetworking operation has been proposed in a copending European Patent Application xe2x80x9cA Method for Improving High Speed Traffic Operation in an Internet Environment and System for Implementing said Methodxe2x80x9d, filed on . . . (FR998010), and assigned to the same Assignee. This application enables speeding up internetworking by providing the network and more particularly the routers with self bridging facilities dynamically converting the used router connections into bridged connections during traffic operation. In other words, transparent bridging is performed, as required, by dynamically building up Bridge tables into the routers establishing direct level 2in-out connections. While the best mode of implementation addresses Ethernet LANs, the invention applies to routers inter-connecting most LANs, including so-called Token Ring. But as far as Token ring LANs are concerned the proposed solution is not optimal.
One object of this invention is to enable improving high speed data transfers in an internet environment by using Internet Protocol (IP) intelligence as well as Token-ring facilities to optimally drive self-bridging configuration of conventional routers.
Another object of this invention is to enable improving high speed data transfers in an internet environment by using IP intelligence and Token ring specifications to enable optimally self configuring routers into bridges, dynamically, during data traffic on the specific paths used for connections toward a designated target host.
A further object of this invention is to enable improving high speed data transfers in an internet environment requiring only limited broadcasting to enable self-configuring routers into bridges.
Another object of this invention is to provide a solution for efficiently self configuring routers into bridges on paths set between source and target hosts respectively attached to different token-rings.
The foregoing and other objects, features and advantages of this invention will be made apparent from the following more detailed particular description.
This invention deals with a method for improving high speed traffic operation in an internet environment using standardized protocols of the so-called Internet Protocol (IP) suite, by speeding up data packet transfers between a source host (S) attached to a first Token ring Local Area Network (LAN) (N1), and a target host (T) within a subnet attached to a different Token ring LAN (N2), both LANs being interconnected by a router (R) establishing connections at OSI Standard network level (layer 3) through use of an IP table, by dynamically setting, during traffic operation, a single virtual LAN.
The source host (S) encapsulates the first packet to be sent with a conventional Token ring header including RMAC as destination Media Access Control (MAC) address of R, SMAC as source MAC address and an empty Routing Information Field (RIF) as layer 2 information, and IP address of T (TIP) as layer 3 information.
Upon receiving the first packet, router R reads its IP table for best match with TIP address whereby the subnet including T is identified. The net handler runs an ARP protocol to identify TMAC address, stores it in its ARP table, substitutes MAC header with said TMAC address into said first packet destination MAC address field and forwards said first packet over N2. Router R then sends a conventional Internet Control Message Protocol (ICMP) over N1 as limited broadcast, whereby all hosts, including S, add a direct route toward T""s subnet on their interface to N1; R configuring itself in Proxy ARP for the defined subnet.
The second packet is passed by S to its N1 interface with TIP address. S runs a conventional Address Resolution Protocol (ARP) by sending an ARP request carried over an All Route Broadcast (ARB) with TIP address over N1 and R answering with RMAC address and the RIF data leading to N2. Then the second packet is sent over N1 with TMAC, SMAC, the defined RIF and TIP data.
Upon receiving the second packet, the router R bridging function identifies RIF data, and bridges the packet to its net handler toward N2. Router R""s net handler runs an ARP process to substitute R""s MAC address to TMAC address.